Phenolic compounds are useful for the synthesis of useful organic compounds such as couplers for colorant uses. Useful compounds include those having a substituted first amino group in the 2-position and a substituted second amino group in another position such as the 5-position of the phenol. One example of such useful compounds is a phenolic coupler useful as a cyan dye-forming coupler in a silver halide imaging process. To obtain the desired hue, they contain the requisite two amino groups including a ballast in one of the two groups. A ballast is a hydrophobic group having 8 or more aliphatic carbon atoms which serves to keep the coupler and resulting dye within the hydrophobic dispersion in which it is present so that it will not be washed out during the aqueous processes associated with development.
There have been available two processes for obtaining the desired phenol compounds. In the first, a phenol is provided with an amine group in the two position and a nitro group in the other desired amino position. The 2-position is converted to the desired amino substituent using acid chloride. Then, the nitro group is reduced to amine and the second amine group is converted to the desired amino substituent using acid chloride. It would be desirable to avoid it use of nitroaminophenol compounds for safety reasons since such materials present an explosion concern. Further, this method is limited in the order of introducing the substituents to the molecule.
Another method is described by Mitsunori Ono in "Heterocycles", 27(4), 881, (1988). The use of 2-alkyl-6-nitrobenzoxazoles is suggested to prepare the desired 2,5-dicarbonamido phenols. The examples employ a 2-t-butyl group, and it was found that an attempt to hydrolyze the oxazole ring in acid to deblock the 2-position was unsatisfactory and "all attempted usual acid cleavage . . . failed." Ono is ultimately concerned with effecting a reaction at the 4-position of the phenol ring rather than effecting a conversion of the nitro group, so the use of alkaline KOH hydrolysis is of no concern. But if one does desire to convert the nitro group, as in the present case, there is a major concern, because the use of alkaline KOH deblocking will also initiate undesired side reactions at the converted nitro site.
It is desirable to develop a process that provides a simple and safe way to prepare 2,5-dicarbonamido phenol compounds in good yield.